The Home Secretary has told thousands of rank-and-file police there is a risk that victims of crime will stop ringing 999 because they are afraid of being sued by officers.

Her warning follows criticism of a number of police officers who are seeking damages against people for injuries sustained while attending suspected crime scenes. Addressing the annual Police Federation conference in Bournemouth, Theresa May said she wanted to bring an end to "frivolous" legal claims made against the public.

Receiving a more restrained reception than last year, when she was confronted by heckling and calls to resign, Mrs May also pledged to change the law so criminals who kill police officers face minimum whole-life jail terms.

Earlier this year it emerged a Norfolk Constabulary officer was seeking damages from a petrol station owner after she reportedly tripped on a kerb while attending a suspected break-in. Police Constable Kelly Jones's lawyers claim the property owner is at fault after she injured her leg and wrist when she was called to Nun's Bridges Filling Station in Thetford, Norfolk, in August last year.

Mrs May told the event in Bournemouth: "I know that the vast majority of you are dedicated public servants of the best kind. But when a police officer sues a member of the public because they slipped on private property - that is simply not the sort of attitude police officers should exhibit.

"I want to work with the federation to make sure police officers don't make frivolous claims. Not least because it would be quite wrong if people become reluctant to call the police for fear of being sued."

Speaking to reporters at the conference centre after her appearance, Mrs May added: "The public are saying they don't want a situation where they feel that they don't want to ring 999, they don't want to call the police, because they're worried they're going to get sued."

Mrs May told the conference that the Government is to propose that the starting point for anyone convicted of the murder of a police officer in the line of duty should be increased to whole-life without parole from a current minimum of 30 years.

Receiving a round of applause from officers in attendance, Mrs May said: "The murder of a police officer is a particularly appalling crime. To attack and kill a police officer is to attack the fundamental basis of our society."

There have been 12 direct killings of police officers in the course of duty since 2000 - including the murder of Pcs Fiona Bone and Nicola Hughes by Dale Cregan in Greater Manchester last year.